Second-half goals from Fernando Llorente and Carlos Tevez proved enough to clinch the points for the champions at the Stadio Armando Picchi.
The result lifted Antonio Conte's side two points clear of Roma, who play Cagliari on Monday night, and left the Amaranto 16th in the table.
Inter Milan lost ground on the leaders as they were held 1-1 at struggling Bologna.
The visitors fell behind to Panagiotis Kone's 12th-minute goal, with Jonathan levelling in the 51st minute.
The point left Inter in fourth place, two points behind Napoli and eight behind Juventus.
It was also a disappointing day for Fiorentina, who went down 1-0 at Udinese.
The hosts stifled the threat of Giuseppe Rossi to snatch victory thanks to Thomas Heurtaux's first-half goal.
Defeat left La Viola in fifth, two points adrift of Inter.
Sinisa Mihajlovic was denied a first win as Sampdoria boss as Lazio earned a 1-1 draw thanks to Lorik Cana's late equaliser.
Third-bottom Samp, playing with 10 men since the 46th minute, looked to be heading for an important win after substitute Roberto Soriano gave them a 67th-minute lead, but they were undone deep in stoppage time.
Sampdoria's Nenad Krsticic was shown a straight red card for a two-footed tackle on Cristian Ledesma.
The two dropped points saw the Genoa side remain in the bottom three, a point behind Bologna.
Lazio remain winless on the road this season and are eighth in the standings.
Torino ended an eight-match winless run in style with a 4-1 triumph over Catania, who dropped to the foot of the table on goal difference.
Goals from Ciro Immobile and Omar El Kaddouri gave the hosts a commanding 2-0 half-time lead at the Olympic stadium in Turin.
Substitute Sebastian Leto pulled a goal back shortly after the restart, but Emiliano Moretti swiftly restored Torino's two-goal cushion before El Kaddouri sealed matters on the hour mark.
Ten-man Sassuolo won 2-0 at home to Atlanta, Simone Zaza putting them on their way in the 63rd minute and Domenico Berardi adding the second soon after.
Sassuolo kept out their opponents, despite playing the final 14 minutes with a man less after defender Luca Antei was sent off for a second booking.